Visual Criteria for Solder Joint Acceptance A visual acceptance criterion is a sentence and a photograph, and the two have to agree. Where they do not, the criterion is interpreted differently by different inspectors, and the difference shows up as an inconsistent yield rather than as a defect. What the…

PCB Conveyor Maintenance: Design and Assembly Considerations Electronics manufacturing has become a discipline of small details. Solder paste volumes, placement accuracy, temperature profiles and inspection limits all add up to the final result. This guide looks at PCB conveyor maintenance from the perspective of a PCBA factory floor, covering maintaining…

Impedance Test Method Verification An impedance test is a measurement, and a measurement has an uncertainty. Verifying the test means establishing what the instrument, the probe and the coupon contribute, so that a reading outside tolerance is a real excursion rather than a change in the measurement. What the Measurement…

Sizing Thermal Via Arrays Under High Power LED Pads An LED converts only part of its input into light, and the rest becomes heat that has to leave through the board. Thermal vias are the standard way to move that heat from the pad under the die to a copper…

Solder Paste Expiry and Mixing Solder paste is a chemically active material with a shelf life, a thawing requirement and a working life in the printer, and treating it as a consumable that is either in date or out of date misses most of what affects the print. Two jars…

Wire and Cable Assembly in Box Build Wiring inside an enclosure is the part of assembly where a mistake is most expensive to find. A crimp that is not fully inserted, a wire routed over a sharp edge or a connector latched into the wrong position may pass an electrical…

Hand Soldering Tip Selection and Care The soldering tip is the heat source, and most hand soldering problems that are attributed to technique are actually problems of heat transfer. A tip that is too small, too worn or too heavily oxidised cannot deliver enough energy to the joint, and the…

Destructive Failure Analysis Methods for PCB Assemblies Some failures cannot be seen from the outside. A cracked joint under a ball grid array, a delaminated interface, a void at the die attach and a crater in the laminate all require the assembly to be opened before the cause can be…

Reflow Conveyor Support, Sag and Vibration A reflow oven carries the board through the zones on a conveyor, and the board is supported only at its edges or not at all. At reflow temperature the laminate is softer than it is at room temperature, and what happens to the board…

PCB Conveyor Plan: A Practical Review for Manufacturing Teams Electronics manufacturing has become a discipline of small details. Solder paste volumes, placement accuracy, temperature profiles and inspection limits all add up to the final result. This guide looks at PCB conveyor plan from the perspective of a PCBA factory floor,…